How to check if variable is an object or an array?

Question

I have a problem that i didn't know how to solve it, i have test some information of how i should comparing or checking a variable if it was an array or an object

I have tried this

console.log({} == []); // return false
console.log({1:"haha"} == {}); // return false
console.log(["haha"] == {}); // retun false

The problem is, that i want to know if a variable is actualy an object cause typeof of both [] or {} return object.

console.log(isobject({1:"haha"})) // should return true;
console.log(isobject(["haha"])); // should return false;

Or

console.log(isobject({})) // should return true;
console.log(isobject([])); // should return false;

Is there any function to check variable like above? Thanks for any correction.

array instanceof Array //Output true , can also check is it array or not — Jameel Moideen, Nov 10 '18 at 04:14

Vignesh Raja · Accepted Answer · 2018-11-15T11:10:08.080

9

This would help.

var a = [], b = {};

console.log(Object.prototype.toString.call(a).indexOf("Array")>-1);
console.log(Object.prototype.toString.call(b).indexOf("Object")>-1);

console.log(a.constructor.name == "Array");
console.log(b.constructor.name == "Object");

There are many other ways, but the above is backward compatible in all browsers.

Related questions must be referred:

Check if a value is array

Check if a value is object

edited Nov 15 '18 at 11:10

answered Nov 10 '18 at 04:03

Vignesh Raja

7,927
1
33
42

1

Why the `indexOf` check, and not just a plain comparison? You can also check the name of the constructor – CertainPerformance Nov 10 '18 at 04:13
how can i check the name of the constructor? @CertainPerformance – Irvan Hilmi Nov 15 '18 at 10:59
@IrvanHilmi Updated the answer. – Vignesh Raja Nov 15 '18 at 11:11
@IrvanHilmi eg `[].constructor.name === 'Array'` (though `Array.isArray` is better for arrays) and `({}).constructor.name === 'Object'` – CertainPerformance Nov 15 '18 at 11:24

score 5 · Answer 2 · answered Nov 10 '18 at 04:01

5

arr = [1,2,3]

Array.isArray(arr) // should output true

for object I would do obj = {a:1}

Object.keys(obj).length // should output 1

so you could do

Object.keys(obj).length >= 0 // should be true if obj is obj literal.

answered Nov 10 '18 at 04:01

jack blank

5,073
7
41
73

1

_`Object.keys(obj).length` // should output 1_ `arr = [5]` will also output 1 for `Object.keys(arr).length` – Lucas S. G. Nov 25 '22 at 15:25

score 1 · Answer 3 · answered Aug 22 '21 at 17:16

var jsonData = {
  Name:"Jonh Doe",
  Dept: {
    code: "cse",
    title: "Computer science & tech"
  },
  Courses: [
    {
      code: "cse123",
      name: "something"
    },{
      code: "cse123",
      name: "something"
    }
  ]
}

for(var item in jsonData){
  if(typeof jsonData[item] === "object"){
    var x = "";
    if(Array.isArray(jsonData[item])) x = "Array";
    else x = "object";
    console.log(item + " is " + x);
  }else{
    console.log(item + " is " + typeof jsonData[item]);
  }  
}

score 1 · Answer 4 · edited Aug 23 '22 at 09:41

1

JSON.stringify(variable).startsWith("[")

This will return true when variable is an array.

JSON.stringify(variable).startsWith("{")

This will return true when variable is an object.

edited Aug 23 '22 at 09:41

vimuth

5,064
33
79
116

answered Aug 18 '22 at 18:50

Mayur Gudi

25
2

How to check if variable is an object or an array?

4 Answers4